Electric Field‐Induced Cell Membrane Permeabilization and Gene Transfer: Theory and Experiments

The permeabilization and gene transfer phenomena in terms of the effect of electric field and cell parameters are reviewed in this paper. Electropermeabilization designates the use of short high‐voltage pulses to overcome the barrier of the cell membrane. A position‐dependent modulation of the membrane potential difference is induced, leading to a transient and reversible local membrane alteration. The electro‐induced permeabilization is long lived. A free exchange of hydrophilic molecules takes place across the membrane. The fraction of the cell surface which is competent for exchange is a function of the field intensity. The level of local exchange is strongly controlled by the pulse duration. This permeabilized state can be used to load cells with a variety of different molecules, either through simple diffusion in the case of small molecules, or through a multi‐step process as is the case for DNA transfer involving the electrophoretically driven association of the macromolecule with the destabilized membrane and its subsequent passage. Electropermeabilization is now in use for the delivery of a large variety of molecules: from ions to drugs, dyes, tracers, antibodies, oligonucleotides, RNA and DNA. While most studies are performed in vitro in cells in culture, an increasing number of data are obtained in vivo on tissues. However, membrane molecular and cell metabolic changes remain for the most part poorly understood. Therefore it is of great importance to elucidate the underlying phenomena both for the in vitro use of the method in terms of efficiency but also for the in vivo use of the method in terms of security.     

低能离子束介导转基因技术

通过与常规的植物转基因方法进行比较,阐述了低能离子束介导转基因的原理和优点,以及该技术自开创以来在应用领域中取得的成果。     

Hypoglycemic activity of polysaccharide, with antioxidation, isolated from cultured Cordyceps mycelia

Cordyceps sinensis, a well-known traditional Chinese medicine, possesses anti-tumor, immunostimulant and antioxidant activities; however, the identities of active components have not been determined. In our previous study using antioxidant activity-guided fractionation [Li et al., 2003. A polysaccharide isolated from Cordyceps sinensis, a traditional Chinese medicine, protects PC12 cells against hydrogen peroxide-induced injury. Life Sci. 73, 2503-2513], a polysaccharide of molecular weight approximately 210kDa was isolated from cultured Cordyceps mycelia by ion-exchange and sizing chromatography. The isolated polysaccharide, named CSP-1, which has strong anti-oxidation activity, contains glucose, mannose and galactose in the ratio of 1:0.6:0.75. In the present study, we demonstrated the hypoglycemic effect of CSP-1 on normal and alloxan-diabetic mice and streptozotocin (STZ)-diabetic rats. The basal glucose level did not differ significantly among the normal mice. CSP-1 (at 200 and 400mg/kg body wt./day for 7 days, p.o.), however, significantly reduced the blood glucose level by 12.0+/-3.2% and 22.5+/-4.7% in normal mice, respectively (p<0.05). When administered at a dose of higher than 200mg/kg body wt. daily for 7 days, CSP-1 produced a significant drop in blood glucose level in both STZ-induced diabetic rats and alloxan-induced diabetic mice. The serum insulin levels in diabetic animals were also increased by administration of CSP-1 (p<0.05). CSP-1 with hypoglycemic properties increased circulating insulin level in diabetic animals, which suggests that CSP-1 may stimulate pancreatic release of insulin and/or reduce insulin metabolism.     

A locus on mouse Chromosome 9 (Adip5) affects the relative weight of the gonadal but not retroperitoneal adipose depot

To identify the gene or genes on mouse Chromosome 9 that contribute to strain differences in fatness, we conducted an expanded mapping analysis to better define the region where suggestive linkage was found, using the F₂ generation of an intercross between the C57BL/6ByJ and 129P3/J mouse strains. Six traits were studied: the summed weight of two adipose depots, the weight of each depot, analyzed individually (the gonadal and retroperitoneal depot), and the weight of each depot (summed and individual) relative to body size. We found significant linkage (LOD = 4.6) that accounted for the relative weight of the summed adipose depots, and another for the relative weight of the gonadal (LOD = 5.3) but not retroperitoneal (LOD = 0.9) adipose depot. This linkage is near marker rs30280752 (61.1 Mb, Build 34) and probably is equivalent to the quantitative trait locus (QTL) Adip5. Because the causal gene is unknown, we identified and evaluated several candidates within the confidence interval with functional significance to the body fatness phenotype (Il18, Acat1, Cyp19a1, Crabp1, Man2c1, Neil1, Mpi1, Csk, Lsm16, Adpgk, Bbs4, Hexa, Thsd4, Dpp8, Anxa2, and Lipc). We conclude that the Adip5 locus is specific to the gonadal adipose depot and that a gene or genes near the linkage peak may account for this QTL. The following sequences have been submitted to the GenBank database: Thsd4: Accession Nos. DQ424862 and DQ517441 and Lsm16: Accession Nos. DQ240818-DQ240819.     

A potential native natural enemy of invasive aquatic weed – water hyacinth

A potential native natural enemy of invasive aquatic weed water hyacinth was found in Shanghai of China: Chironomus larva. The larva can dig into the bulbiform petiole of water hyacinth, the petiole will be broken and decomposed soon, and also, the canker of water hyacinth will fall off. So this larva will be a native natural enemy of water hyacinth for controlling its invasion. From other side, water hyacinth will be gradually naturalized to a component of native ecosystem, although it maybe needs a long time.     

Poly-γ-glutamate from Bacillus subtilis inhibits tyrosinase activity and melanogenesis

Poly-γ-glutamate (γ-PGA) has been considered as one of the most promising biomaterials with a wide range of applications, but there has been no report that directly shows the anti-tyrosinase and anti-melanogenesis properties of γ-PGA. In the present study, we investigated the inhibitory effects of γ-PGA with low molecular weight (Mw; lγ-PGA) and high Mw (hγ-PGA) on mushroom tyrosinase and murine tyrosinase activities and on melanogenesis in B16 melanoma cells. First, we showed that both lγ-PGA and hγ-PGA could effectively inhibit mushroom tyrosinase activities including monophenolase and diphenolase activities in a dose-dependent manner. Second, both lγ-PGA and hγ-PGA showed strong anti-tyrosinase activity and anti-melanogenesis in B16 melanoma cells. Third, both lγ-PGA and hγ-PGA inhibited forskolin-induced tyrosinase activity and melanogenesis by decreasing the levels of intracellular reactive oxygen species and nitric oxide while increasing the catalase activity in B16 cells. This is the first report on the anti-melanogenesis effect of γ-PGA, which suggests that γ-PGA could have a potential in the cosmetic skin whitening business, therapeutic applications and the food industry.     

Zinc Transporter 7 Induced by High Glucose Attenuates Epithelial-to-Mesenchymal Transition of Peritoneal Mesothelial Cells

Zinc (Zn) is an essential micronutrient and cytoprotectant involved in preventing many types of epithelial-to-mesenchymal transition (EMT)-driven fibrosis in vivo. The zinc-transporter family SLC30A (ZnT) is a pivotal factor in the regulation of Zn homeostasis. However, its function in EMT in peritoneal mesothelial cells (PMCs) remains unknown. This study explored the regulation of zinc transporters and the role they play in cell EMT, particularly in rat peritoneal mesothelial cells (RPMCs), surrounding glucose concentrations and the molecular mechanism involved. The effects of high glucose (HG) on zinc transporter gene expression were measured in RPMCs by real-time PCR. We explored ZnT7 (Slc30A7): the effect of ZnT7 over-expression and siRNA-mediated knock-down on HG-induced EMT was investigated as well as the underlying molecular mechanisms. Over-expression of ZnT7 resulted in significantly inhibited HG-induced EMT in RPMCs, while inhibition of ZnT7 expression using a considerable siRNA-mediated knock-down of RPMCs increased the levels of EMT. Furthermore, over-expression of ZnT7 is accompanied by down-regulation of TGF-β/Smad pathway, phospho-Smad3,4 expression levels. The finding suggests that the zinc-transporting system in RPMCs is influenced by the exposure to HG. The ZnT7 may account for the inhibition of HG-induced EMT in RPMCs, likely through targeting TGF-β/Smad signaling.